Objectives: The aim of this study was to validate an ultrasound protocol for evaluating the anterolateral ligament of the knee. Methods: A Thiel technique cadaveric specimen was used to validate an optimal scanning position and develop an ultrasound protocol to evaluate the anterolateral ligament. Three musculoskeletal sonographers acquired short- and long-axis images of the anterolateral ligament in 36 knees from 18 healthy volunteers. Anterolateral ligament length, thickness, width, and distance between anterolateral ligament insertion and lateral tibia plateau were measured. Intraclass Correlation Coefficient (ICC) was calculated. Results: The inter-rater reliability for anterolateral ligament thickness was poor, ICC = 0.35 (95% CI: –0.06–0.63). The inter-rater reliability for anterolateral ligament length and width was good, ICC = 0.80 (95% CI 0.64–0.89), ICC = 0.88 (95% CI 0.79–0.94), respectively; and the inter-rater reliability for the distance between insertion and lateral tibia plateau was excellent, ICC = 0.96 (95% CI 0.93–0.98). Conclusions: Ultrasonography is a reliable method for evaluating the anterolateral ligament. There is an excellent reliability for the distal part of the anterolateral ligament. As injuries usually occur in this part of the ligament, this protocol may be used to evaluate the anterolateral ligament in patients with suspected anterior cruciate ligament tears in clinical practice.